there have been many threads on this. Try Brasso, available anywhere in the cleaning aisle. It's a very mild abrasive for cleaning metals. Rub some in with a soft cloth, LET IT DRY, then buff off. May take a couple of applications, but it'll take out smaller scratches and make bigger scratches a lot less noticable. You can use it on both the front and back (just don't get any in the cracks, it's impossible to get out)
pnw